Title: Memory across Eye-Movements: 1/f Dynamic in Visual Search Authors: Deborah J. Aks Department of Psychology University of Wisconsin - Whitewater Whitewater, WI 53190 Gregory Zelinsky Department of Psychology State University of New York Buffalo, NY Julien C. Sprott Department of Physics University of Wisconsin - Madison Madison, WI 53705 PURPOSE. The presence of apparently random behavior in visual search (e.g., Horowitz & Wolfe, 1998) has led to our proposal that the human oculomotor system may have subtle deterministic properties that underlie its complex behavior. We report the results of one subject's performance in a challenging search task in which 10,215 fixations were accumulated. METHOD & RESULTS. A number of statistical and spectral tests revealed both fractal and 1/f structure. First, scaling properties emerged in differences across eye positions and their relative dispersion (SD/M)--both decreasing over time. Fractal microstructure also emerged in an Iterated Function Systems test and delay plot. Power spectra obtained from the Fourier analysis of fixations produced brown (1/f2) noise and the spectra of differences across eye positions showed 1/f (pink) noise. CONCLUSION. While the sequence of absolute eye positions resembles a random walk, the differences in fixations reflect a longer-term dynamic of 1/f pink noise. These results suggest that memory across eye-movements may serve to facilitate our ability to select out useful information from the environment. The 1/f patterns in relative eye positions together with models of complex systems (e.g., Bak, Tang & Wiesenfeld, 1987) suggest that our oculomotor system may produce a complex and self-organizing search pattern providing maximum coverage with minimal effort. Contact Info: -- Deborah J. Aks Psychology Dept Univ of Wisconsin - Whitewater Whitewater, WI 53190 http://psych.uww.edu/aks/ aksd@mail.uww.edu 262-472-2257 (w)